Utilization of Landfill Gas towards High-BTU Methane and Low-Cost Hydrogen Fuel

1. Utilization of Landfill Gas towards High-BTU Methane and Low-Cost Hydrogen Fuel by Manolis M. Tomadakis and Howell H. Heck Florida Institute of Technology Melbourne, FL 32901

2. Outline • Rationale • Objectives • Methodology • Preliminary Results • Anticipated Benefits

3. Rationale • H2S is among the components of landfill gas, which contains primarily CO2 and CH4 • Photolytic decomposition of H2S provides an alternative source of hydrogen fuel • Removal of H2S from landfill gas would help prevent odors, hazards and corrosion • Removal of CO2 would increase the BTU value of the remaining methane gas

4. Objectives 1. Test the efficiency of molecular sieves 4A, 5A, 13X in separating landfill gas towards high-BTU methane and FSEC- quality H2S (>50% H2S and <1% CO2) by Pressure Swing Adsorption (PSA) 2. Investigate the effect of the landfill gas H2S content on the PSA process efficiency, by varying the H2S feed volume fraction in the range 0-1 %

5. Objectives (cont’d) 3. Determine the effect of pressure on CH4 and H2S product recovery and purity, by varying the system high pressure in the range 40-100 psig. 4. Examine the effect of near-equilibrium operation of the PSA process on the percent utilized sieve capacity and overall process efficiency, by varying the gas feed flowrate.

6. Pressure Swing Adsorption System Layout

7. Pressure Swing Adsorption Apparatus

8. Experimental MethodologyColumn I 1. Pressurization to the desired adsorption pressure by pure CH4 2.  Adsorption - supplying a mixture of CH4, CO2 and H2S 3.   Blowdown to the initial pressure (~1 atm) 4.   Desorption - purging with inert N2 at nearly atmospheric pressure

9. Experimental MethodologyColumn II 1. Pressurization to the selected adsorption pressure by the adsorption product of column I or a directly supplied mixture of CO2/H2S 2.  Adsorption at the desired high pressure 3.   Blowdown to the initial pressure 4.   Desorption by purging with inert N2 at nearly atmospheric pressure

10. Preliminary Testing 1. Molecular Sieves 13X and 4A were packed in Columns I and II, respectively 2. A mixture of CH4-CO2-H2S was supplied to Bed I to separate CH4 3. A mixture of CO2-H2S was supplied to Bed II to separate CO2 and recover H2S 4. Adsorption and desorption in Beds I & II were carried out at 100 psig & 0 psig, respectively

11. Preliminary Experiments

12. Ratio of Outlet to Inlet Molar Flow during Adsorption

13. Ratio of Inlet to Outlet Molar Flow during Desorption

14. Gas Product Composition in Bed I during Adsorption

15. Gas Product Composition in Bed I during Desorption

16. Gas Product Composition in Bed II during Adsorption

17. Gas Product Composition in Bed II during Desorption

18. H2S/CO2 Molar Ratio in Bed II Desorption Product

19. Sieve Capacity & Utilization 1. Column I adsorption loads: 0.9 kg CH4, 2.4 kg CO2, & 2 kg H2S/100 kg 13X Column I sieve equilibrium capacities: 23 kg CO2 or 19 kg H2S per 100 kg 13X 2. Column II adsorption loads: 2.8 kg CO2 and 1.9 kg H2S per 100 kg 4A Column II sieve equilibrium capacities: 18 kg CO2 or 14 kg H2S per 100 kg 4A

20. Summary of Preliminary Results 1. A 50% CH4 feed over 13X ZMS resulted to 98%-99% product CH4 during adsorption 2. A 68% CO2 - 32 % H2S feed over 4A ZMS resulted to 71% H2S and 29% CO2 product during desorption 3. A 20-30% utilization of equilibrium sieve capacity was encountered

21. Expected Technical Resultsof Proposed Study Variation of the PSA product purity and recovery (CH4%, H2S%, CO2%) and utilized % sieve capacity with: a) Type of utilized molecular sieve (4A, 5A, 13X) b) H2S content of landfill gas (0-1%) c) Maximum applied pressure (40-100 psig) d) Landfill gas feed flowrate

22. Anticipated Benefits Development of environmentally acceptable & financially sound end use for landfill gas, providing both a high-BTU CH4 stream and a low-cost H2S feed stream supply for the FSEC renewable hydrogen fuel program